Laccase and Melanization in Clinically Important Cryptococcus Species Other than Cryptococcus neoformans

The laccase enzyme and melanin synthesis have been implicated as contributors to virulence in Cryptococcus neoformans. Since isolations of Cryptococcus species other than C. neoformans from clinical specimens have been increasing, we examined the laccase activities of C. albidus, C. laurentii, C. curvatus, and C. humicola. Incubation of cells with epinephrine produced adrenochrome color in C. albidus, C. laurentii, and C. curvatus but not in C. humicola. Activity was always less than in C. neoformans. Laccase was detected in the soluble fractions of disrupted C. albidus, C. laurentii, and C. curvatus cells. Activity staining of partially purified enzyme after nondenaturing polyacrylamide gel electrophoresis revealed that laccases from C. albidus, C. laurentii, and C. curvatus migrated more slowly than that from C. neoformans. One strain of C. curvatus exhibited two melanin bands. Thus, several clinically emerging Cryptococcus species express laccase and can synthesize melanin.